Special thanks to Darren Tanke for his highly informative email on
septic bites in theropods etc. As Darren emphasises, I think we
should all be careful to distinguish between venomous bites and
septic bites. Graeme has now kindly provided the source for the
printed speculation that _Neovenator_ may, perhaps like many other
theropods, have possessed a septic bite. Therefore, though the
suggestion was not included in the original paper (Hutt et al. 1996),
it _has_ been attibuted to one of the authors of this paper. Thus
Graeme should not have gotten any of the blame.. apologies if it
seemed that way Graeme.
A concern I have about speculations on the behaviour of animals
(incl. theropods) with septic bites is that many people are now
assuming that these animals specifically killed THANKS TO their
septic bites. Even in _Varanus komodoensis_, the importance of 'death
by infection' behaviour is controversial and, judging by field
observations made by Auffenberg and others, certainly not the usual
method of killing used by the lizards. Raking wounds caused by teeth
and claws, partial disembowelment, 'hamstringing', and exsanguination
and concomitant shock all seem more normally employed by Komodo
monitors, and certainly the effects are more immediate.
In a related email, Dan Varner, the dean of contemporary mosasaur
restoration, wrote..
> My question is about the Gland of Gabe, which I have been told is the poison
> gland in the lower jaw of the varanoid Helodermids like the Gila
> Monster. Could this have been present in mosasaurs? Could it have
> been present in archosaurs?
To inject or otherwise conduct venom into the tissues of a bitten
animal (either prey or an aggressor or perceived threat), animals
generally need hollowed syringe-like teeth, as in viperid and elapid
snakes, or teeth with base-to-tip grooves. The absence (to my
knowledge!) of such modified teeth in mosasaurs strongly indicates
that they could not / did not conduct venom. However, tooth
base-to-tip grooves have now been reported in a number of basal
archosauriform teeth - most notably in _Uatchitodon_ (as described by
Hans Sues in _JVP_) and strongly indicate a venomous bite in
these animals. A few more venomous archosauriforms are in press at
the present time.
Incidentally, an obscure speculation that _Iguanodon_ may have had a
poisonous gland at the base of its thumb spike, and hence may have
injected venom into predators with this weapon (Tweedie 1977) is
effectively disproven by the absence of any similar structures (viz.,
base-to-tip grooves or hollowed out body with hollow tip) in the
iguanodont thumb spike.
While on the subject, Tweedie's (1977) book also includes another
bizarre idea: that, because there were (according to Tweedie) almost
immobile and highly vulnerable to predators when on the ground,
azhdarchid pterosaurs must have had some form of chemical repellant
with which to protect themselves. _Quetzalcoatlus_ was therefore
visualized as a gigantic pterosaurian skunk. The full ref for this
wonderful book is..
TWEEDIE, MICHAEL 1977. _The World of the Dinosaurs_. Weidenfeld &
Nicolson (London), pp. 143.
To return to the injection of venom during biting, there is a
disclaimer in that not all venomous biters do have hollow-tipped or
groove-bearing teeth. Certain soricids (shrews) (and other
insectivores*) are now known to possess true venom glands in the
mouth, but they are only able to transfer the venom to the tissues of
the prey during violent chewing: they literally have to invade the
prey's tissues so that venom will be chewn into the wound. The
evolution of this behaviour might be explained by the fact that some
of the shrews that practise it the most, notable _Neomys_, the water
shrews, catch and then immobilize prey that are nearly as large / as
large as they are, i.e. frogs.
Bakker's speculations about the presence of venomous bites in
theropods can be found in..
BAKKER, R.T. 1993. Bakker's Field Guide to Jurassic Park Dinosaurs.
_Earth_ 2 (5), pp. 33-43.
Writing about the theropod _Procompsognathus_, Bakker says..
"In Jurassic Park, compys have poisonous saliva, used to
numb the face, hands and feet of prey. This is plausible: some dino
descendants (birds) have nerve toxins today, and a narcotizing
bite has evolved in many other species, such as toads." (Bakker
1993, p. 33)
This ignores the fact that only ONE bird is known to have nerve
toxins, and that species with narcotising bites - toads, snakes,
lizards - all reveal clear dental/osteological features indicating
that they do. No theropod does.
Also of incidental interest is that fact that in the same article,
Bakker suggests that, because hadrosaurs appear defenceless in the
face of tyrannosaurian predators, they quite probably possessed some
defensive capability we do not yet know of - perhaps they secreted
noxious chemicals, he suggests. I will not comment on this, but I'm
almost certain that it inspired the behaviour of a _Parasaurolophus_
in a 2000 A.D. comic series. The story was about a girl who lived
together with a tyrannosaur, a dromaeosaur, a parasaurolophus, and a
giant dimorphodontid pterosaur. The _Parasaurolophus_ was able to use
a 'psycho-chamaeleon' skill, and become invisible to predators,
psychically blending into the surrounding vegetation!
*The name Insectivora has arguably won out over Lipotyphla.
"If you don't say what you know, no one will know what you know, you
know"
DARREN NAISH
darren.naish@port.ac.uk